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May 2012

Volume 83, Issue 5, Articles (05xxxx)

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Rev. Sci. Instrum. 83, 051101 (2012); http://dx.doi.org/10.1063/1.4709621 (18 pages)

Igor Lubomirsky and Oscar Stafsudd

The periodic pulsed heating technique for measuring pyroelectricity (the Chynoweth method) is one of several measurement techniques that have been significantly enhanced through advances in instrumentation such as fast digital averaging oscilloscopes and modulated light sources.

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back to top Condensed Matter; Materials

A furnace with rotating load frame for in situ high temperature deformation and creep experiments in a neutron diffraction beam line

H. M. Reiche, S. C. Vogel, P. Mosbrucker, E. J. Larson, and M. R. Daymond

Rev. Sci. Instrum. 83, 053901 (2012); http://dx.doi.org/10.1063/1.4708619 (7 pages) | Cited 2 times

Online Publication Date: 2 May 2012

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A resistive furnace combined with a load frame was built that allows for in situ neutron diffraction studies of high temperature deformation, in particular, creep. A maximum force of 2700 N can be applied at temperatures up to 1000 °C. A load control mode permits studies of, e.g., creep or phase transformations under applied uni-axial stress. In position control, a range of high temperature deformation experiments can be achieved. The examined specimen can be rotated up to 80° around the vertical compression axis allowing texture measurements in the neutron time-of-flight diffractometer HIPPO (High Pressure – Preferred Orientation). We present results from the successful commissioning, deforming a Zr-2.5 wt.% Nb cylinder at 975 °C. The device is now available for the user program of the HIPPO diffractometer at the LANSCE (Los Alamos Neutron Science Center) user facility.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
62.20.Hg Creep
81.40.Lm Deformation, plasticity, and creep

Development of a simultaneous Hugoniot and temperature measurement for preheated-metal shock experiments: Melting temperatures of Ta at pressures of 100 GPa

Jun Li, Xianming Zhou, Jiabo Li, Qiang Wu, Lingcang Cai, and Chengda Dai

Rev. Sci. Instrum. 83, 053902 (2012); http://dx.doi.org/10.1063/1.4716459 (7 pages)

Online Publication Date: 14 May 2012

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Equations of state of metals are important issues in earth science and planetary science. A major limitation of them is the lack of experimental data for determining pressure-volume and temperature of shocked metal simultaneously. By measuring them in a single experiment, a major source of systematic error is eliminated in determining from which shock pressure release pressure originates. Hence, a non-contact fast optical method was developed and demonstrated to simultaneously measure a Hugoniot pressure-volume (PH-VH) point and interfacial temperature TR on the release of Hugoniot pressure (PR) for preheated metals up to 1000 K. Experimental details in our investigation are (i) a Ni–Cr resistance coil field placed around the metal specimen to generate a controllable and stable heating source, (ii) a fiber-optic probe with an optical lens coupling system and optical pyrometer with ns time resolution to carry out non-contact fast optical measurements for determining PH-VH and TR. The shock response of preheated tantalum (Ta) at 773 K was investigated in our work. Measured data for shock velocity versus particle velocity at an initial state of room temperature was in agreement with previous shock compression results, while the measured shock data between 248 and 307 GPa initially heated to 773 K were below the Hugoniot evaluation from its off-Hugoniot states. Obtained interfacial temperatures on release of Hugoniot pressures (100–170 GPa) were in agreement with shock-melting points at initial ambient condition and ab initio calculations of melting curve. It indicates a good consistency for shock melting data of Ta at different initial temperatures. Our combined diagnostics for Hugoniot and temperature provides an important approach for studying EOS and the temperature effect of shocked metals. In particular, our measured melting temperatures of Ta address the current controversy about the difference by more than a factor of 2 between the melting temperatures measured under shock and those measured in a laser-heated diamond anvil cell at ∼100 GPa.
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07.20.Dt Thermometers
07.20.Ka High-temperature instrumentation; pyrometers
42.79.Bh Lenses, prisms and mirrors
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Stencil mask methodology for the parallelized production of microscale mechanical test samples

Paul A. Shade, Sang-Lan Kim, Robert Wheeler, and Michael D. Uchic

Rev. Sci. Instrum. 83, 053903 (2012); http://dx.doi.org/10.1063/1.4720944 (6 pages) | Cited 1 time

Online Publication Date: 21 May 2012

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A new methodology to parallelize the production of micromechanical test samples from bulk materials is reported. This methodology has been developed to produce samples with typical gage dimensions on the order of 20–200 μm, and also to minimize the reliance on conventional focused ion beam fabrication methods. The fabrication technique uses standard microelectronic process methods such as photolithography and deep-reactive ion etching to create high aspect ratio patterned templates—stencil masks—from a silicon wafer. In the present work, the stencil mask pattern consists of a linear row of tensile samples, where one grip of each sample is integrally attached to the bulk substrate. Once fabricated, the stencil mask is placed on top of a pre-thinned substrate, and the pattern and substrate are co-sputtered using a broad ion beam milling system, which ultimately results in the transfer of the mask pattern into the substrate. The methodology is demonstrated using a Si stencil mask and a polycrystalline Ni foil to manufacture an array of metallic micro-tensile samples.
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06.60.Ei Sample preparation (including design of sample holders)
07.10.Cm Micromechanical devices and systems
81.16.Nd Micro- and nanolithography
81.20.Wk Machining, milling
85.40.Hp Lithography, masks and pattern transfer

A full Stokes vector ellipsometry measurement system for in situ diagnostics in dynamic experiments

L. Bakshi, S. Eliezer, G. Appelbaum, N. Nissim, L. Perelmutter, and M. Mond

Rev. Sci. Instrum. 83, 053904 (2012); http://dx.doi.org/10.1063/1.4717675 (11 pages)

Online Publication Date: 23 May 2012

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A fast ellipsometry system with a resolution of only a few nanoseconds that can simultaneously measure all four Stokes parameters was developed for use in dynamic experiments. Due to its fine temporal resolution, the system is useful for a wide variety of dynamic setups, two of which are presented, fast foil heating and shock compression. As a test case the optical properties of nickel were measured in a fast foil heating setup. The complex index of refraction and emissivity at 532 nm and in the range of 1000–1900 K are presented. It was found that the emissivity monotonously increases below and above the melting point while an abrupt increase of about 2% was observed at the phase transition. These results are in accordance with the literature. Shock compression experiments included sample-free surface measurements. Samples of 1020 steel were shocked up to 25 GPa on the Hugoniot curve. The measured optical properties under these conditions showed a significant change; the value of the emissivity was doubled.
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07.60.Fs Polarimeters and ellipsometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments

Jun Lin and Megan T. Valentine

Rev. Sci. Instrum. 83, 053905 (2012); http://dx.doi.org/10.1063/1.4719916 (5 pages) | Cited 1 time

Online Publication Date: 24 May 2012

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We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1–1800 pN to ∼4.5 μm paramagnetic beads using magnet-bead separations in the range of 0.3–20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ∼1 kPa.
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85.70.Ay Magnetic device characterization, design, and modeling
06.20.fb Standards and calibration
75.50.Ww Permanent magnets
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

Magnetic measurements at pressures above 10 GPa in a miniature ceramic anvil cell for a superconducting quantum interference device magnetometer

Naoyuki Tateiwa, Yoshinori Haga, Tatsuma D. Matsuda, and Zachary Fisk

Rev. Sci. Instrum. 83, 053906 (2012); http://dx.doi.org/10.1063/1.4722945 (5 pages) | Cited 1 time

Online Publication Date: 31 May 2012

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A miniature ceramic anvil high pressure cell (mCAC) was earlier designed by us for magnetic measurements at pressures up to 7.6 GPa in a commercial superconducting quantum interference magnetometer [N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011)]10.1063/1.3590745. Here, we describe methods to generate pressures above 10 GPa in the mCAC. The efficiency of the pressure generation is sharply improved when the Cu-Be gasket is sufficiently preindented. The maximum pressure for the 0.6 mm culet anvils is 12.6 GPa when the Cu-Be gasket is preindented from the initial thickness of 300–60 μm. The 0.5 mm culet anvils were also tested with a rhenium gasket. The maximum pressure attainable in the mCAC is about 13 GPa. The present cell was used to study YbCu2Si2 which shows a pressure induced transition from the non-magnetic to magnetic phases at 8 GPa. We confirm a ferromagnetic transition from the dc magnetization measurement at high pressure. The mCAC can detect the ferromagnetic ordered state whose spontaneous magnetic moment is smaller than 1 μB per unit cell. The high sensitivity for magnetic measurements in the mCAC may result from the simplicity of cell structure. The present study shows the availability of the mCAC for precise magnetic measurements at pressures above 10 GPa.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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